• Corrosion Science and Technology
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• v.20 no.1
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• pp.7-14
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• 2021

PosMAC^® is a brand of Zn-Mg-Al hot-dip coated steel sheet developed by POSCO. PosMAC^® can form dense surface oxides in corrosive environments, providing advanced corrosion resistance compared to traditional Zn coatings such as GI and GA. PosMAC^® 3.0 is available for construction and solar energy systems in severe outdoor environments. PosMAC^®1.5 has better surface quality. It is suitable for automotive and home appliances. Compared to GI and GA, PosMAC^® shows significantly less weight reduction due to corrosion, even with a lower coating thickness. Thin coating of PosMAC^® provides advanced quality and productivity in arc welding applications due to its less generation of Zn fume and spatters. In repeated friction tests, PosMAC^® showed lower surface friction coefficient than conventional coatings such as GA, GI, and lubricant film coated GA. Industrial demand for PosMAC^® steel is expected to increase in the near future due to benefits of anti-corrosion and robust application performance of PosMAC^® steel.

• Transactions of Materials Processing
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• v.18 no.4
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• pp.304-309
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• 2009

Quenchable boron steel is a new type of high strength steel to reduce the weight of automobiles and maintain the safety conditions. Quenchable blanks can be hot-stamped and hardened in a water-cooled tool to achieve high strength. In this paper, new alloy for hot stamping is designed based on requirement of mechanical properties and two types of surface coating are investigated in viewpoints of oxidization and exfoliation. An automotive part of center pillar is manufactured by hot-stamping using Al-Si coated sheet. The performance of developed part is compared by static compression test and side impact crash test.

• Advances in Energy Research
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• v.8 no.3
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• pp.155-163
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• 2022

The current study presents experimental research on a parabolic trough collector with tube and cavity receivers. The primary concentrating parabolic reflector is designed for an aperture area of 2×2 m² with mirror-polished stainless steel sheet reflectors. The cavity receiver consists of a compound parabolic secondary reflector and a copper tube. Both the conventional tube receiver and the cavity receiver tube are coated with black powder. The experiments are carried out to compare the efficiency of the cavity receiver with the tube receiver for fluid temperature rise, thermal efficiency, and overall losses. The experiments showed significantly higher fluid temperature rise and overall efficiency and lower thermal losses for the cavity receiver compared to the tube receiver within the parameters explored in this study.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.202-210
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• 2016

This study was intended to investigate the effect of the amount of magnesium addition and heat treatment in the Al-Mg coating film in order to improve corrosion resistance of aluminum coating. Al-Mg alloy films were deposited on cold rolled steel by physical vapor deposition sputtering method. Heat treatment was fulfilled in an nitrogen atmosphere at the temperature of $400^{\circ}C$ for 10 min. The morphology was observed by SEM, component and phase of the deposited films were investigated by using GDLS and XRD, respectively. The corrosion behaviors of Al-Mg films were estimated by exposing salt spray test at 5 wt.% NaCl solution and measuring polarization curves in deaerated 3 wt.% NaCl solution. With the increase of magnesium content, the morphology of the deposited Al-Mg films changed from columnar to featureless structure and particle size was became fine. The x-ray diffraction data for deposited Al-Mg films showed only pure Al peaks. However, Al-Mg alloy peaks such as $Al_3Mg_2$ and $Al_{12}Mg_{17}$ were formed after heat treatment. All the sputtered Al-Mg films obviously showed good corrosion resistance compared with aluminum and zinc films. And corrosion resistance of Al-Mg film was increased after heat treatment.

• Transactions of Materials Processing
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• v.31 no.4
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• pp.186-193
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• 2022

The application of UHSS sheet is being expanded up to 50% to reduce the weight of automobiles and improve safety. However, due to the high strength and low elongation of the ultra-high tensile strength steel sheet, product defects such as spring back and mold defects such as cracks and chippings also occur. In this study, Pin/Ring on Disc and Spiral wear tests were conducted to evaluate the durability of Ti/Cr-coated molds for forming 1.2GPa grade UHSS sheets. Component analysis and thickness were measured for each coating layer, and hardness and adhesion were investigated to determine mechanical properties. Combining the results of various wear tests, it was found that the TiAlN coating had the best wear and sticking resistance.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.44-44
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• 2018

칼라도장강판은 금속 제품의 제품화 공정 중에 도장 공정을 생략함으로 경제적이며, 제조공정 중 발생할 수 있는 VOCs(Volatile Organic Compounds)의 배출 염려가 없어 건축 및 가전 산업에 다용되고 있다. 칼라도장강판은 용융아연도금강판(GI), 전기아연도금강판(EGI), 용융알루미늄아연합금도금강판 등이 기재로 적용되고 있으며, 최근 마그네슘 성분이 첨가되는 고내식 도금강판 개발과 함께 고내식 도금강판을 이용한 칼라도장강판의 개발 및 수요 발굴을 위한 연구가 활발하게 진행 중에 있다. 칼라강판의 구성은 일반적으로 도막 밀착성 확보를 위한 화성처리층, 기재와 도막간의 밀착성과 내식성 개선을 위한 하도층(primer layer), 가공성, 내오염성, 의장성 등의 기능성 부여를 위한 상도층(top layer)의 구조로 도장되어 있다. 도료는 가공성, 내오염성, 경도 등의 기능성이 우수한 폴리에스테르 수지계가 가장 폭넓게 사용되고 경화제로는 멜라민 화합물과 이소시아네이트 화합물이 널리 사용되고 있다. 칼라도장 강판은 1970년대 이후 본격적으로 보급되어 사용되기 시작하였으며, 화성처리층은 밀착성과 내식성이 우수한 크로메이트처리가 널리 사용되고, 하도층은 방청성이 우수한 크로메이트계 방청 안료를 함유시킨 도료가 일반적이다. 그러나, 전기전자 제품에 적용되는 칼라도장강판은 2006년에 RoHS 규제의 시행과 더불어 6가 크롬 사용 제한의 영향으로 크롬프리 화성처리가 일반화되어 적용되고 있으며, 그 동안 6가 크롬 제안이 유보적이었던 건축용 칼라도장강판 또한 크롬프리 화성처리층 및 크로메이트계 방청 안료의 하도층 적용을 회피하고 있는 추세이다. 이에 따라, 고내식 합금도금강판을 기재로 사용하고 기존의 화성처리층과 하도층에 크롬프리 수지를 적용하는 연구개발이 활발하게 진행 중에 있다. 본 연구에서는 마그네슘이 첨가된 고내식 합금도금강판으로 Al-Mg-S i강판과 용융 Zn-Al-Mg 합금도금강판에 기존의 상용화 공정에서 사용되는 크롬계 및 크로프리 화성처리 적용 칼라도장강판에 대한 내식성 등 칼라도장강판의 특성에 대해 발표한다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.37-38
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• 2011

알루미늄은 높은 내부식성과 우수한 물리적 특성으로 철강 제품의 부식방지를 위한 표면처리와 항공 우주분야 소재로 각광을 받아왔다. 알루미늄을 철강 제품의 부식방지를 위한 표면처리 소재로 사용되는 경우 비교적 두껍게(15 ${\mu}m$ 이상) 코팅된다. 본 연구에서는 얇은 두께(3 ${\mu}m$ 이하)의 알루미늄 박막을 이용하여 높은 내식성을 갖는 코팅 공정을 개발하고자 한다. 물리기상증착으로 코팅되는 대부분의 금속은 주상정 구조를 갖는다. 주상정 구조는 grain boundary에 공극이 존재하고, 이 공극을 통해서 부식을 일으키는 물질이 보호막과 모재의 계면으로 침투하여 모재가 부식을 일으킨다. 스퍼터링 공정을 제어하여 알루미늄 박막의 공극 발생을 억제하여 보호막으로서의 기능을 향상할 수 있는 방법을 제안한다. 알루미늄 코팅을 위해서 magnetron sputtering을 이용하였으며, 기판은 냉연강판을 사용하였다. 냉연강판위에 코팅된 알루미늄 박막을 분석한 결과, 스퍼터링 소스에 역방향 자기장을 인가하여 코팅한 알루미늄 박막이 염수분무 120 시간 후에도 적청이 발생하지 않는 우수한 내식성을 보였다.

• Korean Journal of Metals and Materials
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• v.49 no.4
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• pp.281-290
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• 2011

In order to gain better understanding of the selective surface oxidation and its influence on the galvanizability of a transformation-induced plasticity (TRIP) assisted steel containing 1.5 wt.% Si and 1.6 wt.% Mn, a model experiment has been carried out by depositing Si and Mn (each with a nominal thickness of 10 nm) in either monolayers or bilayers on a low-alloy interstitial-free (IF) steel sheet. After intercritical annealing at $800^{\circ}C$ in a $N_2$ ambient with a dew point of $-40^{\circ}C$, the surface scale formed on 590 MPa TRIP steel exhibited a microstructure similar to that of the scale formed on the Mn/Si bilayer-coated IF steel, consisting of $Mn_{2}SiO_{4}$ particles embedded in an amorphous $SiO_{2}$ film. The present study results indicated that, during the intercritical annealing process of 590 MPa TRIP steel, surface segregation of Si occurs first to form an amorphous $SiO_{2}$ film, which in turn accelerates the out-diffusion of Mn to form more stable Mn-Si oxide particles on the steel surface. During hot-dip galvanizing, particulate $Fe_{3}O_{4}$, MnO, and Si-Mn oxides were reduced more readily by Al in a Zn bath than the amorphous $SiO_{2}$ film. Therefore, in order to improve the galvanizability of 590 TRIP steel, it is most desirable to minimize the surface segregation of Si during the intercritical annealing process.